Fear toward God (3:18) has several meanings. On the positive side, fear implies reverence for God. That reverence includes an awareness of His power, His glory, and His holiness. True worship is an outgrowth of such reverential fear (see e.g. Isa. 6:5). When we see who God is we will not only realize His greatness, but also our own poverty. As in the case of Isaiah, awe of God will lead us to worship and serve Him.  

In Proverbs 1:7 we read that “the fear of the Lord is the beginning of knowledge” (RSV). People don’t even fear God. They don’t even have wisdom’s starting point. People would do well to have a healthy fear of him who will determine their eternal destiny. It is unfortunate that most people in our culture fear their neighbour’s opinion more than they do God. They fear their boss or financial destitution more than the Lord.  

Paul has finished stringing OT pearls together. Now, in v19, he anticipates a question from his Jewish readers because whatever unfavourable texts we find in the OT, the Jews would always apply to the gentiles. They felt exempt from the common condition of humanity.  Condemnation is always for others. After all, don’t I go to church every week, pay my tithe, live a good clean life, and read my Bible? This is the logic that he smashes in v19.  

The law (the entire OT teachings) is aimed at those who are under it – that is, the Jews /churchgoers. And what do those Bible texts in Rom.3:10-18 prove? That you stand condemned! The reference to the stopped mouth evokes the image of the defendant in court, who, when given the opportunity to speak in his own defence, remains silent, overwhelmed by the weight of evidence against him. There is nothing to do but wait for the pronouncement and execution of the sentence. “The whole world will be held accountable to God.”  

We can thank God that v19 is not the end of the book of Romans. It is rather the last text before the most important passage. With v21 Paul will begin to set forth God’s solution to the sin problem